chore(quic-interop): inspect — list every file in case dir first

Layout varies by runner version; print the tree so we can see what
the runner actually wrote (qlog/pcap/log filenames, sizes) before
guessing at paths.

quic/interop/inspect-multiplexing.sh

@@ -29,6 +29,11 @@ if [[ -z "$CASE_DIR" ]]; then
 fi
 echo "==> case dir: $CASE_DIR"
 
+echo
+echo "=============== file tree under case dir ==============="
+find "$CASE_DIR" -maxdepth 4 -type f -printf '%s\t%p\n' 2>/dev/null \
+    || find "$CASE_DIR" -maxdepth 4 -type f -exec ls -l {} + 2>/dev/null
+
 echo
 echo "=============== client/log.txt (tail) ==============="
 tail -n 200 "$CASE_DIR"/client/log.txt 2>/dev/null \